Nick Timiraos reports on the presidential race.

North Dakota Sen. Byron Dorgan endorsed Barack Obama today, adding his name to the list of Democrats from red states that have endorsed the Illinois senator.

Dorgan said he joined colleagues such as Arizona Gov. Janet Napolitano and Kansas Gov. Kathleen Sebelius who are “really anxious to have a candidate on the top of the ticket who isn’t going to give up on a state before it begins.”

North Dakota voted for President Bush by a 63% to 36% margin over Sen. John Kerry in 2004, and Dorgan noted how his state had voted for a Democratic president just twice in the last century — for Franklin D. Roosevelt and Lyndon Johnson.

Dorgan credited Obama, who won 62% of the state’s caucus vote, with turning out twice as many Democrats as Republicans in the state’s Feb. 5 caucuses. “There’s something unusual happening here,” he said. Dorgan, who as a senator is also a superdelegate, said that he waited until after his state’s Feb. 5 primary to endorse a candidate in order to “watch the developments.”

Obama picked up the endorsement of Connecticut Sen. Chris Dodd Tuesday, giving him back-to-back endorsements from Democratic heavyweights. Clinton has been endorsed by 13 of her Senate colleagues compared with 10 for Obama.

Dorgan is close friends with former South Dakota Sen. Tom Daschle, one of Obama’s earliest backers, and has been one of the fiercest Senate critics of free trade, including the North American Free Trade Agreement. He said the fact that Obama “has always opposed Nafta” was a major factor in his endorsement.

Obama has sparred with rival Sen. Hillary Clinton of New York as they race for blue-collar voters in Ohio, where Nafta remains unpopular, and Obama has tried to portray his Senate colleague as someone who supported Nafta after her husband signed the landmark free trade agreement into law in 1993 but opposed it once she decided to run for president.

In a conference call today, Dorgan blamed Nafta for turning a “very small trade surplus with Mexico into a huge trade deficit.” He pointed to Nabisco Corp.’s decision to move production of its Fig Newton cookies to Monterrey, Mexico, from New Jersey, saying it must have been cheaper to “shovel fig paste” in Mexico. Dorgan pushed last year to block funding of a pilot program by the Department of Transportation allow long-haul Mexican trucks on U.S. roads.